MEMORANDUM 

From: The Office of Air Quality Planning and Standards 

 U.S. Environmental Protection Agency 

To: EGU NSPS Docket (EPA-HQ-OAR-2013-0603) 

Date: June 2014 

Subject: Coal Cleaning and Upgrading 

Introduction 

Low-rank coals (lignite and subbituminous) are often used because the low cost per unit of heat input 

relative to bituminous coal and the low sulfur content. However, a major disadvantage of low-rank coals 

is their high moisture content, typically 25 to 40%. When this coal is burned, considerable energy is 

required to vaporize and heat the moisture, thus reducing the efficiency of the EGU. As fuel moisture 

decreases, the heating value of the fuel increases so that less coal needs to be fired to produce the same 

amount of electric power. Drier coal is also easier to handle, convey, and pulverize – reducing the 

burden on the coal-handling system. In addition, an EGU boiler (and the corresponding control 

equipment) designed for dried coal is smaller and has lower capital costs than a comparable EGU 

designed to burn coal that has not been dried. The pre-combustion drying of low-rank coals can improve 

the overall efficiency and several advanced coal drying technologies are available. 

Coal upgrading is a term used to describe processes that reduce the moisture content of the coal and that 

create a stable product that avoids spontaneous combustion and moisture reabsorption. The final product 

from these coal upgrading processes have a higher heating value and generally emit less pollutants. The 

following is a brief summary of some of the coal upgrading technologies, including propriety 

technologies. This summary is not intended to be a comprehensive list of available technologies. The 

performance values given here are those that have been provided by the technology provider in 

publically available sources. Inclusion of a technology in this summary is not intended to be an 

endorsement of that technology by the US EPA or the US Government. Figure 1 shows the estimated 

heat rate impact of coal heating value as estimated by the National Coal Council1

 and the Integrated 

Environmental Control Model.2 

Figure 1: Impact of Coal Quality on Heat Rate 

                                                            

1 National Coal Council, “Opportunities to Expedite the Construction of New Coal‐Based Power Plants,” (2004). Available at:

http://www.nationalcoalcouncil.org/Documents/ExpediteNov30rpg.pdf. 2 Download available from: http://www.cmu.edu/epp/iecm/
Coal Upgrading Technologies 

Advanced Coal Conversion Process 

Rosebud SynCoal Partnership’s Advanced Coal Conversion Process (ACCP) was one of the first largescale coal upgrading projects in the US. ACCP was co-sponsored by the United States Department of 

Energy (DOE) Clean Coal Technology Demonstration Program (CCTP). The process consisted of two 

thermal reactors, one to evaporate water and the other to remove chemically bound water, and a third 

physical cleaning stage to cool and separate mineral matter and SynCoal product. The demonstration 

facility operated for 9 years. Various coals were processed for a variety of customers. Records indicate 

the SynCoal was able to improve boiler efficiency at some power plants by 1-4%, along with reductions 

in NOX, ash, and sulfur. While the SynCoal product quality was as expected, the product was not able to 

incorporate a cost-effective way to stop spontaneous combustion. 

BCB technology 

White Energy’s binderless coal briquetting (BCB) technology upgrades subbituminous and lignite coals 

and coal fines through a thermal drying process followed by physical and chemical stabilization through 

a binderless briquetting process. The BCB process produces stable transportable briquettes with a lower 

moisture content and corresponding higher heating value than the original feed coal. White Energy has 

constructed the Cessnock Demonstration and Production Plant in Australia allowing the company to 

demonstrate and test the process on potential clients’ fuel sources. In the future, White Energy plans to 

refine the process for bituminous fuel, as well. 

Exergen Technology 

Exergen’s Continuous Hydrothermal De-watering (CHTD) technology has been developed for lignite 

and high-moisture subbituminous coals. CHTD is a decarboxylation reaction with high heat and pressure 

followed by a separation process. The process has been tested on a small pilot plant that has proven 

successful. The company has plans to build a demonstration plant, continue testing new fuel sources, 

and further research and development projects. 

GEO-COAL 

Total Sinergy International’s (TSI) GEO-COAL removes moisture from low-rank coals, primarily 

lignite, via heat provided from gasifying the coal fines. The first step in the process crushes the coal. All 

coal fines are separated and sent to the gasification burners, while the remaining coal continues to the 

drying area. The gasifiers provide super-heated steam to drive out the moisture, then the product is 

cooled. The Indonesian company has a coal upgrading plant in Indonesia that has successfully tested the 

upgrade capabilities on many different coals. They market three different coals, GEO-LITE, GEO-HI, 

and GEO-MET based on the product quality. TSI has signed an agreement with the Indonesian national 

utility company to use GEO-COAL technology at their facility. They are marketing their products to 

Asia, Australia, Indonesia and India. 

GTLEnergy Technology 

GTL Energy has developed a technology to upgrade low rank coals and biomass. The process is a low 

temperature process that removes moisture content. The resultant product is a coal briquette. In the case 

of their biomass and coal test, the result was a wood and coal mix briquette. The product has been tested 

on different coals from around the world. The company has a demonstration plant in North Dakota and 

has just completed construction on a plant in New Zealand. 

K-Fuel® 

Evergreen Energy’s K-Fuel® process removes moisture and mercury from the coal through heat and 

pressurization of low rank coals (lignite and subbituminous). The final product (K-Fuel®) has a higher 

heating value, lower mercury content, is physically and chemically stable, and can be handled and 
transported similar to untreated coal. A commercial plant and testing lab in Gillette, Wyoming have 

processed and tested a variety of low rank fuels from different countries. A few power plants have been 

host to test burns of the K-Fuel® product to validate the combustion benefits. The company’s latest 

announcements indicate pursuing investors and clients in Asia and Australia. 

Mechanical Thermal Expression 

Mechanical Thermal Expression (MTE) is a process in which a coal water slurry is created, then fed into 

a reactor that applies mechanical pressure. The pressure is believed to decrease the pore sizes in the coal 

and also lower the density of the water, so the coal holds less mass. The coal is then dewatered before 

being fed into the boiler. MTE has been tested in the lab on various coals from Indonesia, Australia, 

Germany and India. 

PristineTM

Clean Coal Energy Inc.’s PristineTM is a continuous process where coal is heated gradually in an inert 

atmosphere, using a set of multi-state heating chambers. The patented multi-stage treatment process 

removes moisture, volatile materials, and contaminants, including organic sulfur, mercury, and 

facilitates the removal of ash. Subbituminous, lignite and metallurgical coal have been tested and proven 

under this process. The volatile chemicals emanating from coal are recovered for useful purposes. The 

methane is returned to the process and used for heating the incoming coal. The light hydrocarbons can 

be used as a fuel source or sold to refiners to be blended with crude oil and refined to produce 

transportation fuels and chemicals. The heavy gases are condensed onto the coal surface and seal the 

openings to limit the ability of the coal to re-absorb moisture or combust spontaneously. The end 

product (PristineTM) maintains the structural integrity of the original coals and is sufficiently rigid to 

withstand the rigors of coal handling and transport, yet requires reduced energy for pulverization at the 

power plant just before combustion. As advancements have been made, Clean Coal Energy Inc. has 

evolved another product, Pristine-MTM, to address problems with their first generation product. 

Construction for a test plant in Oklahoma began as an effort by SAIC and Clean Coal Energy Inc. They 

have been successful in showing efficiency improvements in the testing of over 40 coals. 

Rinker‐England-Skov (RES) coal conversion process 

ConvertCoal, Inc. (CCI) proprietary coal-to-liquids process convert subbituminous and lignite low-rank 

coals into synthetic crude oil and increasing the heating value of the feed coal by approximately 40%. 

In the process, the feed coal is milled to 1⁄4 x 1⁄2-inch, then dried and pyrolyzed at about 1,000°F to 

recover approximately half of the volatile matter as coal-tar oil. The CCI process typically removes 

two-thirds or more of the sulfur and the majority of the volatile mercury and water from the feed coal. 

The CCI Process converts each ton of low-rank coal into approximately 0.8 barrels of synthetic crude oil 

refinery feedstock, 0.5 tons of upgraded coal, and 0.3 tons of water. 

Upgraded Brown Coal 

Kobelco’s Upgraded Brown Coal (UBC) process involves crushing the coal in a grinding mill. Then, the 

coal is mixed with light oil and a heavy oil, before being dewatered. Heat and pressure are applied that 

generates a process vapor containing water and the oil. The next step is a centrifuge to separate the 

slurry cake from any remaining oil before the coal product is briquetted and the oil is recovered for 

reuse. The facility has constructed a demonstration plant that has proven the technical approach to their 

process on lignite coal. The product is stable so that is can be easily transported. They are still in the 

steps of testing the final UBC product. 

Zemag 

The German company ZEMAG Clean Energy Technology GmbH has been marketing and implementing 

their Zemag process to upgrade low rank lignite coal. The process screens and pulverizes lignite coal 

before it is sent to the tubular dryers. In the inclined dryers, the product flows down, while low-pressure 
steam surrounds the tubes for the heat transfer. Following this step, the coal is sent to a press where it is 

briquetted. This process is used in being used at plants in China and Germany. It is an established 

process that provides a stable product.

Coal Drying Technologies 

Densification 

The general densification process takes run-of mine brown coal and mills it to approximately 50 mm 

lumps. These lumps are fed into a low intensity shearing attritioning mill which reduces the particle size 

to approximately 10 μm. This reduction in particle size releases the water that has been trapped within 

the porous structure of the raw coal. The plastic attritioned coal is extruded into pellets or blocks and the 

moist product is conveyed for drying by evaporative loss of water to the atmosphere. Several companies 

have developed variations on this process: 

Environmental Clean Technologies Ltd. has commercialized the COLDRY process, which uses an 

exothermic chemical reaction in combination with waste heat from a co-located power station to dry and 

pelletize brown coal. The final product is stable and can be transported safely. This process can be 

applied to lignite and subbituminous coal. 

Jott Engineering has developed the Jott Solid Fuel Dryer System (JDS), which uses low-grade waste 

energy from the cooling water system at the power plant to dry the plant's solid fuel. This process can be 

used to dry brown coals during the pelletizing process, but is also applicable to other fuel types such as 

biomass solids. The company has acquired patents for the process. 

Pacific Edge Holdings in Austraila has invested in coal drying efforts via La Trobe Lignite 

Development. They have patented a combination of mechanical, thermal and chemical processes that 

can be applied to brown coal for drying before producing a pellet or briquette. The outputs are 

hydrocarbon gases, water and metallurgical coke equivalent. The company focuses on creating these dry 

fuels from lignite for use as metallurgical coals. 

Drycol 

DBAGlobal Australia Pty, Ltd. is developing a coal drying technology with the trade name Drycol. The 

process uses the controlled application of microwave radiation to dry all coal types. Coal feed stock is 

first separated into fine grade coal and one or more larger grades. The fine coal is loaded onto a 

conveyor and conveyed continuously through a microwave-energized heating chamber for drying. The 

fine grade coal is dried sufficiently so that when it is recombined with the larger grade coals, the 

moisture content of the aggregate coal is within a target moisture content range. Microwave energy is 

effective for drying coal because water that is contained with and within the coal is preferentially heated 

rather than heating the coal. Correspondingly the heating rate of coal is much less and linked to heat 

transfer via conduction from water molecules. Provided that the residence time of the coal in the 

microwave applicator chamber is controlled such that the coal temperature remains less than 90°C, there 

is no opportunity for short chain hydrocarbons to volatilize from the coal matrix, and therefore coal 

quality does not degrade. A steel plant in Kentucky hosted a commercial scale test of the product 

showing Drycol’s capability. 

DryFiningTM 

Great River Energy’s DryFiningTM process has been developed at the Coal Creek Station plant, a mine 

mouth lignite-fired plant. The DryFiningTM process passes warm cooling water from the steam turbine 

exhaust condenser through an air heater where ambient air is heated before being sent to a fluidized bed 

coal dryer. The dried coal leaving the fluidized bed is sent to a pulverizer and then to the boiler. Air 

leaving the fluidized bed is filtered before being vented to the atmosphere. 

In addition to using power plant waste heat to reduce moisture, DryFiningTM also segregates particles by 

density. This means a significant amount of higher density compounds containing sulfur and mercury 
can be sorted out and returned to the mine rather than utilized in the boiler. Net gains in overall 

efficiency of 2 to 4% are reported for the process with the lignite heating value increases from 6,200 to 

7,100 Btu/lb. The process has been proven on lignite coal, and the owners are now marketing their 

process within the US and domestically. They also recommend the process for subbituminous fuels. 

MicroCoal®

MicroCoal® Technologies has created MicroCoal® to upgrade lignite. By implementing a microwave 

technology, the original brown coal has reduced moisture and a higher energy value. The facility 

conducted tests and are confident in their product. They have begun construction on commercial 

facilities in Indonesia and are discussing other commercial projects. 

WTA 

RWE Power in Germany is developing a steam fluidized bed drying technology for lignite called WTA. 

A fundamental difference compared to the DryFiningTM process is that the WTA process first mills then 

dries the lignite while the DryFiningTM process first dries then mills the lignite. For the WTA process, 

lignite is first milled to a fine particle size by hammer mills in direct series with a two-stage fluidizedbed dryer. The dried fuel exiting the stationary bed is separated from the gas stream and mixed with 

coarser lignite solids collected from the bottom of the dryer bed and then fed directly to the boiler. The 

heat needed for the drying of the fuel is supplied by external steam, which is normally taken from the 

turbine with the heat transfer taking place in tube bundles located inside the bed. Based on the 

development work completed to date of the WTA technology, the net gain in cycle efficiency is reported 

to be on the order of 4 percentage points, depending on the moisture content of the raw coal and the final 

moisture of the dried lignite. 

Other Technologies 

Other coal drying/upgrading technologies for low-rank coals include: 1) NOAIR and CANONA flash 

heat drying from Green Global Technologies Ltd, 2) high velocity air flow/grinding (e.g., DXCoal’s 

DevourX machine, LF Pumping’s LamiFloTM Drying System), 3) hydrothermal dewatering (wet coal is 

heated under pressure to over 250°C and the coal structure breaks down and shrinks, releasing the water 

as a liquid; e.g., Ignite Energy Resources), 4) heating coarse crushed coal under pressure to 

approximately 200°C (e.g., Aquex), and 5) superheated steam drying (e.g., Pinches Consolidated 

Industries; GEA Process Engineering), and 6) microbial hydrolysis (e.g., Terra Genesis).